The goal of this clinical trial is to learn if the drug istaroxime works to treat mild to moderate cardiogenic shock due to acute heart failure in adults. It will also learn about the safety of istaroxime. The main questions it aims to answer are:
* Does istaroxime relieve participants' shortness of breath compared to a placebo?
* Does istaroxime provide clinical benefit in terms of lowering the risk of dying, having invasive procedures, having worsening heart failure, and/or increasing quality of life compared to a placebo?
* Does istaroxime increase blood pressure compared to a placebo? Researchers will compare istaroxime to a placebo (a look-alike substance that contains no drug) to see if istaroxime works to treat mild to moderate cardiogenic shock due to acute heart failure.
Participants will:
* Receive a 48-hour intravenous infusion of istaroxime or placebo
* Complete questionnaires rating their breathing and describing their quality of life
* Return for a visit 30 and 90 days after the initial drug infusion was started